1. Field Of The Invention
The present invention relates to a printing system that records an object to be printed on a print medium such as paper by using light generated from a laser diode or a light emitting diode as an optical source, and more particularly, to a printing control apparatus which is compatible with a LSU (Laser Scanning Unit) type printing system and a LED (Light Emitting Diode) type printing system.
2. Background Of The Art
Generally, an electrophotographic technique is widely known as the xerography process and its basic principle uses the adsorption force of static electricity and an optical conductive semiconductor whose electric conductivity is varied by light. A printing system using such an electrophotographic technique may be constructed as either a laser scanning unit type or a light emitting diode type, according to the optical source device employed.
The printing system of the laser scanning unit type uses a laser light beam generated from a laser diode as the optical source, by supplying a control signal for controlling the laser diode to a laser scanning unit and uses information generated from a source such as a computer to print data. Meanwhile, the printing system of the light emitting diode type utilizes light generated from a light emitting diode as the optical source by supplying a strobe signal to a light emitting diode array.
Typically, printing control apparatuses used in the printing systems of the laser scanning unit type and the light emitting diode type have different configurations. The reason is that engine control signals that control the laser scanning unit positioned within an engine of the system do not coincide with those controlling the light emitting diode array. Recent efforts in the art however, have sought to use only one type of printing system while seeking a modicum of flexibility in printing. In Printer Controller Apparatus Interfacing With External Data Sources by Kunio Okada, U.S. Pat. No. 5,140,675, separate host and video interfaces are interposed between a printer interface and a laser beam printer in order to endeavor to accommodate printing of image information from both a host computer and another external controller. In the Image Data Processing Apparatus Adaptable To Output Devices Of Different Types, by Haruo Shimizu, described in U.S. Pat. No. 4,691,237 for example, when a laser scan optical unit type printer is connected to an image reader and image information is to be transmitted to that printer, a video signal is supplied to the printer in horizontal synchronization with the beam detect signal, and in other cases such as when inmage information is to be transmitted to a master unit such as an image file controller, the video signal is output in horizontal synchronization with a HSYNC signal generated by the reader. Yoshihisa Kawai in Image Processing Apparatus Operable Analogue And Digital Copying Modes, U.S. Pat. No. 5,099,293 suggests using a light emitting diode array head that can be switched to operated in either a digital copying mode and in an analogue copying mode. The apparatus disclosed by Shimizu '237 and Kawai '293 however, do not address the differences between printing systems. It has been my observation that if the printing control apparatus used in the printing system of the laser scanning unit type is compatible with that used in the printing system of the light emitting diode type, advantages can be expected, such as the reduction of cost by simplifying a manufacturing line, the simplicity of after-sale service and the convenience of use.